While I don't play Badminton (and so can't test with a racket on hand) this seems very cool! I also thought about something similar for judging bikewheel spoke tension - I guess I have to research this a bit more now.
As for monetization: I personally don't have problems with static ads served from your domain. Find some celebrity or brand and ask them if they want to have you serve their banner.
if spokes come in standard guages, it should work for bikewheels as well. There may be some differences due to the bike rim material, but in case of badminton, I found out that frame material could be ignored safely.
As for monetization: I personally don't have problems with static ads served from your domain. Find some celebrity or brand and ask them if they want to have you serve their banner.